1. Field of the Invention
The invention relates to an autostereoscopic image apparatus and, more particularly, to an autostereoscopic image apparatus which can optically transmit an autostereoscopic image by using what is called an integral photography (IP) technique.
2. Description of Related Art
In a conventional apparatus for transmitting a stereoscopic image, generally, an image for the left eye and an image for the right eye which have a binocular parallax are independently transmitted by using a transmitting system such as a coaxial cable or an optical fiber. Even in a multiple-lens autostereoscopic system, generally, an image corresponding to each eye is independently transmitted. Further, in those transmitting methods, usually, the image corresponding to each eye is once converted into an electric signal and is directly transmitted as an electric signal or it is again converted from the electric signal to a photosignal and is transmitted.
On the other hand, as one of autostereoscopic image systems in which an autostereoscopic image can be freely seen from an arbitrary sight point, what is called an integral photography (IP) using a group of convex lenses or a group of pin holes arranged in a plane shape is known. The IP system will now be described hereinbelow.
First, as shown in FIG. 9, a photograph film 3 is put behind a lens group 2 comprising a plurality of convex lenses 2.sub.1, 2.sub.2, . . . , and 2.sub.n arranged on the same plane and a photographing object 1 disposed in front of the lens group 2 is photographed. Images 3.sub.1, 3.sub.2, . . . , and 3.sub.n of the object 1 are formed by the convex lenses 2.sub.1, 2.sub.2, . . . , and 2.sub.n and are photographed, respectively. Subsequently, a photograph which was photographed and developed is arranged at the same position as that of the film when it is photographed for the lens group 2. By seeing the image on the photograph from the position in front of the lens group 2 in this state, an autostereoscopic image can be seen.
The IP system, however, has problems to be improved. FIG. 10 shows a state where a portion near the lens group in the IP system is seen from the top. An image at an object point O1 is formed at a position of P1 by a convex lens L(n) in the lens group. In this case, on the image forming plane, the image lies within a diameter serving as an image pickup region of the convex lens L(n) in the lens group. On the other hand, an image at an object point O2 is formed at a position of P2 by the same convex lens L(n). In this case, the image is formed within a diameter of an adjacent convex lens L(n+1). Further, an image at an object point O3 is formed at a position of P3 by the convex lens L(n+1). The image at the object point O2 and an optical image at the object point O3 overlap and interfere, so that an inconvenience occurs.
Further, a false image in which the convex and concave states are reversed is seen according to the above IP method. Therefore, in order to invert the autostereoscopic image in which the concave shape has been reversed to the convex shape to a normal autostereoscopic image, some means is necessary.
JP-A-9-43539 discloses a 3-dimensional image display apparatus having a lens array in which a plurality of radial type refractive index distributing type lenses are 2-dimensionally arranged so that their optical axes are parallel. It has been described there that by using such a lens array, an autostereoscopic image display apparatus in which lens graininess becomes inconspicuous and good performance is obtained can be easily manufactured. However, drawbacks peculiar to the IP method cannot be solved.
As mentioned above, according to the system in which the image corresponding to each eye is independently transmitted, the transmitting systems as many as only the number of eyes are necessary and a scale of the transmitting system apparatus enlarges. Further, in case of once converting the image corresponding to each eye to the electric signal, the transmitting system apparatus further becomes complicated.
On the other hand, the IP method is a technique which was inherently invented for the purpose of a recording and reproducing method of an autostereoscopic image using a photographic dry plate. If an optical transmission path which is determined by the distance from the principal plane of the convex lens formed in an array shape to the focal plane can be made long, autostereoscopic information can be transmitted. In this case, however, an F value of the lens becomes extremely large and the resolution deteriorates, so that it is actually difficult to realize such a long optical transmission path. Therefore, a normal autostereoscopic image cannot be reproduced on the image receiving side and converting means is additionally necessary. Even if the focal distance of the lens is merely extended, the size of autostereoscopic image cannot be enlarged or reduced and the transmitting system cannot be freely bent as well.